About one-third of older adults have a hearing loss, but fewer than 25% of those who have the problem seek help. Among people with mild to moderate hearing loss, the rate of help-seeking is even lower: 10% or less. There are significant societal ramifications of this situation because untreated hearing problems have been shown to cause social, emotional, and communication difficulties as well as economic disadvantages. Hearing aids are the first and most effective treatment for the hearing loss sustained by most older adults. Thus, it is an important public health priority to increase the hearing aid adoption rate in this group. Several barriers to adoption of hearing aids by older adults have been identified. One of the primary barriers is the cost of the most advanced (premium-level) modern hearing aids, which tend to be about $2000 or more per instrument. Premium-level hearing aids contain the most sophisticated existing technology. However, much less-costly (basic-level) modern hearing aids are available. Basic-level devices include less sophisticated technology but still are very advanced compared to hearing aids available in the past. It is likely that basic-level hearing aids would be substantially helpful for many older adults with mild-moderate hearing loss. But there are very limited independent (i.e., non-manufacturer) data that explore the differences in laboratory and, especially, real world outcomes for patients using basic-level versus premium-level hearing aids, despite the obvious importance of this type of information in promoting evidence-based practice in hearing health care. As a result, when recommending hearing aids to patients, practitioners must rely mostly on unsupported manufacturer claims about feature benefits. Not surprisingly, premium-level devices are very frequently recommended. In this research, the long-term goal is to advance the scientific basis of hearing aid provision for older adults with mild to moderate hearing loss. The effectiveness of basic-level hearing aids and premium-level hearing aids will be determined and compared. In addition, evidence-based guidelines will be formulated to facilitate the selection of the appropriate feature level for a particular individual. The research plan is a blinded, repeated, crossover design. Each participant will complete two crossover trials separated by a washout period. Each trial will feature current hearing aids from one of 6 major manufacturers. In each crossover trial, outcomes will be measured for a basic-level device pair and a matching premium-level device pair. Outcomes will be quantified objectively, by standardized self-report, and qualitatively by interview, in each of four domains: speech understanding, listening effort, localization, and sound acceptability. The results will help practitioners, third-party payers, and informed patients to make more evidence-based decisions about appropriate hearing aids. In the long run, this will improve the cost-effectiveness of hearing aid fittings and support efforts to create and utilize more affordable devices that effectively optimize the listening experience for older adults with mild to moderate hearing loss.